Application Of TiO₂-biochar Composites Based On Thiol-ene Click Chemistry In Water Pollution Control

To overcome the recovery challenge of nanoscale photocatalysts and the drawbacks of existing immobilization methods,in this study,thiol-ene click chemistry,a modular reaction with regioselectivity,was employed to load nano-TiO2 onto biochar,which originated from corn straw and possessed great adsorption capacity.The prepared high avtive product was noted as CC-P25/BC and the essence of excellent performance was revealed compared with impregnation-calcination,sol-gel,solvothermal route.In addition,CC-P25/BC was loaded onto floating carrier through coupling method to further realize practical application,and the preparation parameters were systematically optimized.The main research contents and results are as follows:(1)CC-P25/BC composites were successfully prepared via thiol-ene click chemistry.P25 was not only uniformly loaded on biochar surface,but also established a strong C-S-C chemical connection,which could act as an effective internal electron channel and accelerate the carriers’separation.Thus,CC-P25/BC exhibited excellent adsorption-photocatalytic synergy in the photodegradation of antibiotics and dyes,such as methyl orange(MO)and the product could be easily recyled by membrane filtration.In addition,CC-P25/BC could flexibly adjust the activity by adjusting the ratio of P25 and biochar components,and the degradation process of MO would change along with the activity changes.When P25/BC mass ratio was 6.5:1,CCP25/BC showed the strongest MO degradation,which induced the accumulation of demethylation products and promoted MO photodegradation,finally forming a unique selfaccelerating phenomenon.(2)Superiorities of CC-P25/BC prepared by click chemistry were explored compared with impregnation-calcination,sol-gel,solvothermal route,respectively.CC-P25/BC not only exhibited excellent MO photodegradation in short-term experiments(k values was 1.7,6.7 and 25.4 bigger than three composites),but also exhibited enhanced activity in long-term experiments(2.1,12.2 and 27.7 respectively).And the decrease of TiO2/BC mass ratio after weeklong photoactivity tests was lower,which all exhibited excellent adsorption-photocatalysis synergy and persistent long-term stability.The reason for the best performance of CC-P25/BC were analyzed from the crystal structure,pore structure,light absorption property,and carrier transport.It was found that it was the robust chemical bond between P25 and biochar that endowed CC-P25/BC with the superiority,which not only accelerated the carriers’ separation,but also enhanced the stability of final product.The above results reconfirmed the superiority of click chemistry technology in TiO2 immobilization.(3)Floating CC-P25/BC photocatalytic materials were successfully synthesized by coupling method.By optimizing the type of coupling agent and carrier,the polypropylene(PP)plastic ball based photocatalytic material prepared by titanate coupling agent exhibited the best photoactivity.And the preparation parameters were further optimized as powder concentration at 8 g/L,volume fraction of coupling agent at 50%.Superiorities of CC-P25/BC based PP ball(T-CC-P25/BC@PP ball)were explored compared with P25/BC mixture ball and pure P25 based PP ball.Benefiting from the stable chemical connection between P25 and biochar which synergistically promoted the stable loading of biochar and the effective loading of P25,T-CCP25/BC@PP ball exhibited enhanced adsorption-photocatalysis synergy and stability,which possessed the great practical value.